The Yellowhead or MohuaMohoua ochrocephala is a small insectivorous, bird endemic to the South Island of New Zealand. Recent classification places this species and its close relative, the Whitehead, in the Whistler family Pachycephalidae. The Yellowhead and the Whitehead have sympatric distributions as, conversely, the latter is found only on the North Island and several small islands surrounding it. Although abundant in the 19th century, particularly in beech forests from Nelson and the Marborough Sunds to Southland and Steward Island/Rakiura. They declined dramatically in the early 20th century due to the introduction of black rats and mustelids. Today they have vanished from nearly 75% of their former range. A quarter of the mohua population now lives in the beech forests of the Catlins area.